A common circuit module mounted arrangement for combining a latch and switch (i.e., latch/switch) operation involves a mechanical interaction between a toggle switch on a circuit module and a latch also mounted on the module. As the latch is actuated to lock the circuit module into a support housing, it engages the toggle switch and moves it to successive positions engaging first one then another selected electrical circuit on the module as it is locked into place in the support housing. When the circuit module is removed from the housing, the opening of the latch moves the engaged toggle switch to de-energize the circuit module as it is removed so that no electrical hazard condition occurs as the circuit module is disengaged from the backplane.
A problem with the above arrangement is the required preciseness of the mechanical interconnection between the latch and toggle switch. The difficulty of matching latch positions with toggle switch positions, especially with a three position toggle switch, necessitates strict dimensional tolerances during manufacture adding considerably to the overall cost of the latch/switch mechanism. This latch/switch arrangement is furthermore readily susceptible to mechanical failure in actual field operation, while damage may cause the latch/switch arrangement to partially fail and accordingly fail to de-energize a circuit as expected thereby causing a dangerous electrical hazard. It may, on the other hand, allow electrical power to be applied prematurely to the circuit module resulting in damage to electrical components contained thereon.
It is apparent from the foregoing that a suitable latch/switch arrangement must be readily manufacturable without undue narrow tolerance requirements if it is to be economically viable. It must also be mechanically reliable in providing the necessary sequential circuit connections during insertion and removal operations to minimize electrical hazards and protect circuit components.
Recent manufacturing techniques for printed circuit boards, which may comprise the circuit module, require immersion of the board into a soldering flux during certain stages of manufacturing. This means that a toggle switch may not be installed until all soldering processes have been completed, even though the immersion is for the purpose of completing all electrical connections which include the toggle switch.